The 31-year-old will give up height, weight, reach and a wealth of experience against Rahman who famously floored Lennox Lewis to claim the heavyweight title in South Africa in 2001 but lost the crown in the return fight with the big Brit.
The Super 8 tournament, which has a $500,000 purse, sees eight boxers paired off and they will then meet each other over three three-minute rounds with the winner advancing until an eventual champion is crowned.
One advantage Nansen does possess over Rahman is an intricate knowledge of an eight-man fighting tournament given he is a two-time winner of New Zealand's King of the Ring kickboxing event.
If Nansen can find a way past Rahman he will be well prepared for any later bouts due to his experience with fighting and then resting before climbing back in the ring.
The 41-year-old Rahman (50-8-2) hasn't fought since he was knocked out by Russia's Alexander Povetkin in late 2012 but looked trim when he weighed in at a neat 115kg at SkyCity yesterday, while Nansen tipped the scales at 107.7kg.
"I definitely feel fit," Rahman said. "I'm on my way to getting in the best shape of my life. I'm just taking it one day at a time, keep the ball rolling, go in, win this tournament and get back in the gym on Monday.
"I'm talking trash but I still put in the work and by me putting in the work, I feel confident. I feel supremely confident."
After he weighed in, Rahman predicted he would finish Nansen in the first round but insisted he wasn't getting ahead of himself.
"They all can punch," he said of the field. "Anything can happen, so I'm not taking anybody lightly."
In tonight's other first-round matches, Kiwi Brice Ritani-Coe will meet American Alonzo Butler who is the heaviest fighter in tournament at 134.4kg.
Kali Meehan will square off against Australian heavyweight champion Hunter Sam and Ireland's Martin Rogan will meet two-time UK Prizefighter winner Michael Sprott in the toughest first-round fight.
